An innovative way of growing algae, cleaning wastewater, capturing CO2 and ultimately producing biofuel was developed by OMEGA (Offshore Membrane Enclosure for Growing Algae), a two-year project of the NASA Ames Research Center, CA, USA.
Large, 914 cm (30 ft) long, polyethylene photobioreactors (PBRs) are floating in costal waters. To 1.7 m3 (450 gallons) of domestic wastewater, nutrients, and CO2, Chlorella vulgaris algae were added. The system was equipped with monitoring and control systems so that costs and energy requirements could be estimated, biofouling studied, and impacts on marine animals assessed.
The salt gradient between the seawater and the wastewater drives forward osmosis (FO), which concentrates the nutrients and faciliates algae harvesting. The system uses a third of the energy and recovers 100 % of the water.
The algae grow in the wastewater and remove significant portions of pharmaceuticals and personal care products. When grown in photobioreactors on land, algae get too hot. Floating the photobioreactors in the ocean cools the algae. In the end the algae can be made into biofuel as well as fertiliser and animal feed.
Research now has to focus around upscaling the system and to find the right location to deploy a demonstration system with a protected bay, wastewater, and a source of CO2 nearby. There is also a need for outside funding.
Space-age solutions for wastewater treatment,
Lis Stedmann,
water 21 2012, 21-23.
